ABSTRACT RESEARCH PROJECT 1 Research Project 1 is integrated into the TRANSFORM Center to promote the next generation of research on child maltreatment, translate research findings into clinical and preventive interventions, and disseminate research and best practice to varied stakeholders. Informed by developmental psychopathology, the research incorporates multiple levels of analysis within a lifespan framework. Increasing knowledge of optimal methods for delivering dual mother and child preventive intervention has crucial public health significance in preventing child maltreatment. Project 1 involves a randomized control trial to evaluate whether expanding a Community Health Worker (CHW) outreach model, by adding Child-Parent Psychotherapy (CPP), an intensive intervention that focuses on parent-infant relationships for families at risk for child maltreatment, increases efficacy for improved mother-child relationships, more sensitive parenting, healthier child development, and maltreatment prevention. The efficacy of CPP has been demonstrated with maltreated and other high-risk populations. Through the use of four intervention arms, the evaluation will assess whether more intensive intervention better protects against child maltreatment compared with CHW support alone, and will determine the optimal timing of these interventions (i.e., beginning prenatally or postnatally), the optimal duration of services (i.e., 6 vs. 12 months), mechanisms of effect (mediator analyses), and which intervention strategy works best for mothers with varying risk factors (moderator analyses). Pregnant women (N = 300) and their infants after birth will participate. Longitudinal assessments will occur during the third trimester of pregnancy, at infant's ages of 3 and 9 months, and a post-intervention follow-up at 12 months old. The measurements obtained at each time- point constitute a rich multi-level perspective of maternal and child functioning over time in response to the interventions. Maternal parenting behaviors, representational models, cognitions, and physiological reactivity, and infants' health and development will be assessed longitudinally. CPP groups are hypothesized to improve sensitive and responsive parenting and secure attachment, relative to CHW home visitation alone, thereby reducing risks for child maltreatment. Improvements in maternal attachment representations, parenting cognitions, and stress reactivity are hypothesized to mediate treatment outcomes. Moderators, including maternal histories of trauma, psychopathology, and intimate partner violence, will advance determination of differential responsiveness to CHW and CPP (what works for whom and why?) and allow for tailored preventive strategies. Identification of timing, dosage, and intensity of service delivery, along with outcome mediators and moderators is innovative and will facilitate development of targeted prevention and intervention strategies that support parenting and decrease child maltreatment for this vulnerable population.